Radioisotope study preferred for detection of parathyroid adenoma is?
**Core Concept**
The detection of parathyroid adenoma involves identifying a parathyroid gland that is overproducing parathyroid hormone (PTH), leading to hyperparathyroidism. This can be achieved through various imaging modalities, including radioisotope studies. The preferred radioisotope study for this purpose is one that can selectively identify the parathyroid gland and distinguish it from other thyroid tissue.
**Why the Correct Answer is Right**
The correct answer is **Technetium-99m-sestamibi (Tc-99m MIBI)**, which is a radiopharmaceutical used in a parathyroid scan. Tc-99m MIBI accumulates in both thyroid and parathyroid tissue, but it is rapidly cleared from thyroid tissue, allowing for selective imaging of parathyroid adenomas. This is because Tc-99m MIBI is taken up by the mitochondria of thyroid and parathyroid cells, but it is then cleared from thyroid cells more quickly due to their higher metabolic rate.
**Why Each Wrong Option is Incorrect**
**Option A:** Thallium-201 is not the preferred isotope for parathyroid adenoma detection. While it can be used in combination with Tc-99m MIBI for a dual-phase study, it is not as effective on its own.
**Option B:** Gallium-67 is not typically used for parathyroid adenoma detection. It is more commonly used for imaging infections, inflammation, and certain types of cancer.
**Option C:** Fluorine-18 Fluorodeoxyglucose (FDG) PET/CT is not the preferred imaging modality for parathyroid adenoma detection. While it can be used to identify parathyroid adenomas, it is more expensive and not as sensitive as Tc-99m MIBI scans.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that Tc-99m MIBI scans are more sensitive for detecting parathyroid adenomas when they are performed in a dual-phase manner, with both early and delayed imaging. This helps to increase the accuracy of the scan and reduce false negatives.
**Correct Answer: C. Thallium-201 is not the preferred isotope for parathyroid adenoma detection. While it can be used in combination with Tc-99m MIBI for a dual-phase study, it is not as effective on its own.**